1. Field of the Invention
The present invention relates to an improvement in a slurry seal for sealing a liquid containing a large amount of slurry.
2. Prior Art
A slurry pump heretofore available for pumping up muddy water and other purposes is provided with such a slurry seal as shown in FIG. 2 as its shaft sealing means.
Referring to FIG. 2, that slurry seal is designed in such a way that a stationary seal ring 103 fitted through a packing 102 into a flange 101 located on a pump casing and a rotary seal ring 108 fitted through a packing 107 into a seal cover 106 secured on the outside of an end of a sleeve 105 attached on the outside of a shaft 104 are mutually slid on their sliding planes 103a and 108a while they slide in a close contact with each other, thereby preventing any leakage of a sealing liquid sealed in an outer confined space S leading to an impeller region, not shown, from around the shaft.
The flange 101 is provided with a quenching hole 109 open on a side 113 of the packing 102 located on the outside of the stationary seal ring 103, which is positioned in opposition to the confined space S. Between the inner faces of both seal rings 103 and 108 and the outer face of the sleeve 105 located on the side of the shaft 104, there is provided a baffle sleeve 110 fixed at one end to the inner end of the flange 101 and having the other end extending to an inner-peripheral position of the rear end of the rotary seal ring 108. As a quenching later is supplied through the quenching hole 109 into the side 113 of the packing 102, it flows through a gap 111 located on the outside of the baffle sleeve 110 toward the seal cover 106, whence it is discharged to the atmosphere A through a gap between the baffle sleeve 110 and the sleeve 105.
With such a conventional slurry seal as described above, however, it is known that a slurry of earth and sand or coal powders contained in large quantities in the liquid contained in the confined space S causes a premature wearing-away of the surfaces of the flange 101, both seal rings 103, 108, sleeve 105 and seal cover 106 to contact the confined space S, decreasing service life.
When the flange 101, both seal rings 103, 108, sleeve 105 and seal cover 106 are formed of a high-hardness material With a view to improving their resistance to slurry, there arises a problem that the assembly is hard to manufacture for the very reason of hardness.
In view of the foregoing, an object of this invention is to prevent a premature wearing-away of the surface of a slurry seal assembly to contact a confined space.